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An anonymous reader writes "Ratting someone out' just became much more literal. Dutch police are using trained rats to help keep the streets clean. 'Detective Derrick and his rat partners cost just £8 each and are capable of being trained to identify an impressive range of odors—including drugs and explosives—within ten to 15 days. In contrast, a police dog costs thousands of pounds and requires a minimum training period of eight months. The training procedure is straightforward: the rats are kept in a cage with four metal tea strainers attached inside, one of which contains gunpowder. When the rat recognizes the smell, it is rewarded with a "click" and a small treat. Eventually the rat will learn to move towards the smell instantly. In a demonstration it takes Derrick just two seconds to locate the offending odor."

Likely that would be about as effective with rats as it is with dogs, i.e. not at all. What might work is to use urine from an animal that prey on rats, ferrets in particular come to mind as they are extraordinarily efficient on hunting rodents and therefore it would make sense that rats have an instinctive fear of them.

I find it remarkable and interesting that we still can't or at least not easily produce eith sensors the sniffing capabilities of these critters.

Aside from the fact that the answer would more or less inevitably involve some you-have-fun-fabricating-that micro to nanoscale arrangement of chemical receptors, we labor under the considerable difficulty that we don't really know how scent works.

With something like sight, it's possible to work more or less entirely independently of any real understanding of the eye, human or otherwise, because things like 'primary colors' and color mixing actually work pretty well at handling a wide variety of real-world problems and are simple enough that a decent art curriculum probably covered them before you finished high school. There are certainly horrible complexities ('metallic' isn't a color; but it certainly is a recognizable optical phenomenon, also, please characterize any deviations from the expected result when I take the idealized 24-bit RGB image displayed on my non-ideal 8-bit RBG monitor and send it over to my printer, using CMYK inks...); but 'just put a photosensitive material behind an array of R G and B filters' does actually work. If you proceed to brute-force the hell out of it, it works even better.

With something like scent, we know about plenty of strong and distinctive scents; but nothing 'primary'. Mixing is somewhere between unintuitive and pure black magic, prediction from chemical structures(even if perfectly well defined and provided in whatever form you prefer) is quite difficult outside of a few very well known areas, it's a total mess. Certainly, our ability to (cheaply and quickly, and from very small samples) analyze chemicals in the environment isn't as advanced as we would like; but even if it were, it's not as though we can see ourselves progressing toward the smelloscope, with some technical limitations (as we could in the early days of photography, were basically everything sucked; but basically everything was also precisely analogous to its better-refined contemporary chemical film systems), we'd just be better at identifying molecules flying around in the air.

Which is the goal, ultimately. At least when used to detect drugs, explosives or other illegal substances. So even if it were easier to identify molecules flying around in the air than it is to build a smelling machine, it's easier still to use smelling animals.

The goal is to detect the presence of low amounts of certain molecules related to criminal activity. There is no need to detect scents. So the question is: why are there no cheap and portable detectors that find low concentrations of molecules in the air?
Animal scent is based on vibrations in molecules that dock to receptors in the nose. This allows detection of very low concentrations of molecules. Similar systems can now be created artificially [doi.org].

Animal scent is based on vibrations in molecules that dock to receptors in the nose. This allows detection of very low concentrations of molecules. Similar systems can now be created artificially [doi.org].

There is no compelling evidence that scent (animal or our own) is based upon "vibrations", although such theories do exist. Instead, it seem that odorant molecules bind to receptors in the nose in an analogous way to that by other ligand/receptor pairs, such as neurotransmitters to neurotransmitter receptors. The difference seems to be the most odorant receptors types bind to a range of different odorants. An animal such as s rat has hundreds of different classes of odorant receptor, each of which binds t

I suspect that you could do it (if nothing else, cheat: anti-drug vaccines are a big area of research, so you can probably find somebody to sell you antibodies targeted at any of the major ones, at which point you smear it on a slide and work out a means of detecting antibody/antigen binding...); but that would probably be a good way to discover the other major virtue of animal olfactory systems:

With rather limited exceptions (certain contact anesthetics will temporarily knock the sense of smell offline,

Read the article, they are being used to sense gunpowder, not drugs. For once I actually think the police has got one hell of a new co-worker, the lady that noticed the mine-sniffing rats from the army could also be used in the police force to quickly get an idea if someone had fired a gun or not. I am sure there will still be lab-tests, but at least they can go on with their investigation based on a pretty acurate source.

Presumably rats can be trained to sniff for other substances, as well. It's an open question whether each rat could be trained to detect more than one substance, or detectives would have to carry around a golf bag of rats, each wearing a little jacket labeled with what substance it can sniff. Still, better to carry a golf bag of rats than a golf bag of German shepherds!

It should read "Detective Derrick and his rat partners cost just eight pounds on the head each and are capable of being trained to...". Because while rats don't care about money, they dislike being pounded on the head a lot.

Yeah, but the original story was from wired.co.uk, so the original author converted the cost to UK currency for his intended audience. It does look weird when the story gets re-circulated outside the UK.

The training procedure is straightforward: the rats are kept in a cage with four metal tea strainers attached inside, one of which contains gunpowder. When the rat recognizes the smell, it is rewarded with a "click" and a small treat.

When the wrong one is identified, the gunpowder is ignited. Then training begins for the next rat.